This paper presents experimental and modeling results related to the application of a novel material as a diesel particulate filter substrate. The material, trademarked as INCOFOAM® HighTemp, is a Ni-based superalloy foam. The material can be produced in sheet form with a large range of microstructure parameters. Thanks to the mechanical properties of the sheets, they can be flexibly shaped in various forms. The foam can be washcoated with active catalytic material to promote regeneration.
The experimental testing covers flow and pressure drop behavior with air and exhaust gas, filtration efficiency measurements as function of particle size and regeneration rate measurements. The testing starts from mini-scale reactors and proceeds to real exhaust testing on the engine bench as well as vehicle tests with legislated driving cycles. Special emphasis is given to the characterization of the foam as a catalyst substrate. It is shown that the foam structure exhibits excellent mass-transport properties offering many possibilities for Precious Metal and catalyst volume saving.
A mathematical model is applied to study and understand the filtration and pressure drop mechanisms, as well as surface reactions. The model is validated versus engine experiments. Moreover, CFD studies are also employed to optimize the macroscopic structure of the metal foam filter.
The preliminary results show that the foam filter has a potential for reaching a filtration efficiency of the order of 90% with acceptable pressure drop. This can be accomplished by a proper macroscopic design of the filter, as well as careful selection of the microscopic pore size parameters. For the case of catalyst coated foams, the regeneration rates suggest a superior exploitation of the catalyst compared to conventional coated wall-flow filter concepts.